(57e) Particle Sedimentation in Structured Liquids

Particle sedimentation in liquids is of both fundamental and practical importance.  Most research on the subject has focused on the sedimentation in the absence of an external flow.  However, there are many practical situations where particle sedimentation occurs under flow.  In this study, sedimentation of a particle in various types of structured liquids is studied with and without flow.  The structured liquids include entangled linear polymers, cross-linked polymers, and nanoparticle suspensions.  The sedimentation rate of a single particle in these liquids is measured precisely using a CCD camera and an automatic particle tracking software while the particle is subjected to various flow conditions include steady and oscillatory shear as well as planar elongational flow.  It is found that the static sedimentation rate depends on the low shear viscosity whereas the sedimentation rate under shear depends on the specific flow conditions and viscoelasticity of the sample.  The interplay between the sedimentation, flow type, and viscoelasticity of the sample is discussed.